Vibratory separators are used to separate solid particulates of different sizes and/or to separate solid particulate from fluids. Vibratory separators may be used in the oil and gas industry, in which they are often referred to as shale shakers. Shale shakers or vibratory separators are used to remove cuttings and other solid particulates from drilling mud returned from a wellbore. A shale shaker is a vibrating sieve-like table upon which returning used drilling mud is deposited and through which substantially cleaner drilling mud emerges. The shale shaker may be an angled table with a generally perforated filter screen bottom. Returning drilling mud is deposited at one end of the shale shaker. As the drilling mud travels toward the opposite end, the fluid falls through the perforations to a reservoir below, thereby leaving the solid particulate material behind. Vibratory separators may also be used in the food industry, cleaning industry, waste water treatment, and others.
Shale shakers may have one, two, or three screening decks. In many multi-deck shakers the top deck is a scalping deck designed to remove large heavy solids from the fluid stream before the stream reaches the finer mesh screens. Scalping generally increases screen life and fluid capacity of finer screens. Increasing screen life and fluid capacity may be a large costs savings for a rig. Single deck shakers are lower in cost than multiple deck shakers and are not alone capable of scalping. Although single deck shakers can be used in series to scalp the fluid stream in one shaker before fine screening is done in separate shakers, this requires much more floor space to accommodate multiple shakers. Expensive multiple deck shakers are most often used offshore where there is limited available rig floor space. Despite many valuable contributions from the art, it would be beneficial to develop a screen capable of performing the scalping and fine screening in one deck.